This invention relates to fish-canning machines and particularly to a turret type of solid pack machines such as shown in U.S. Pat. No. 2,542,133 to Gorby, wherein fish loins are moved down a feed chute and filled into metering pockets around the periphery of a rotating turret. The fish in the metering pockets is then compressed and formed into the shape of a can, the fish being then ejected into a can.
Although machines of this general type are used successfully in the fish-canning industry, they have several drawbacks which are of considerable importance to the canner.
First of all, these machines pack fish into one can at a time. The successive operations performed by the machine each take a discrete amount of time and the rate of production is thus dependent upon the length of time required to perform all of these steps. If the rate of production of a fishing packing plant is to be increased, additional machines, with all of their accessory equipment must be installed.
Secondly, the quality of pack is very important, particularly where solid pack tuna is involved. Grading and value of canned tuna are largely determined by the size and proportion of naturally adhering pieces of the original loin or fillet. Canned tuna in solid form, wherein each can contains a preponderance of solid pieces of the loin, constitutes the most generally available top-quality produce. In solid pack tuna the superiority of one pack over another is determined by the general appearance of the pack, the best quality of solid pack being that wherein the fish chunks are packed with the grain being vertical, and in which the chunks are undistorted by pressure and have the least amount of fragments and floating particles. Because of this, it is very desirable that a machine operate in such a manner as to minimize packing pressure and fragmentation of the loins during packing.
In machines of the type shown in the aforesaid U.S. Pat. No. 2,543,133, undesired fragmentation of the loins occurs quite often in the feed chute which leads to the metering pockets. The chute is necessarily restricted in size, since it must be related to the size of the metering pockets, and considerable drag exists between the walls of the chute and the fish therein. The ram which pushes the fish down the chute must exert a correspondingly large force on the fish to overcome this drag, and such force often distorts, mashes or crumbles the fish, detracting from the appearance and lowering the quality of the pack.
Thirdly, control of the weight per can is another important consideration in the use of automatic fish-canning machines. Governmental regulations provide that the labeled weight must be present in the canned product, sometimes on an average weight per half case of 24 cans and sometimes with respect to each can packed. With any automatic canning machine some variations in weight per can will inherently occur. To meet these regulations the machine will be set so that the average weight in the can is sufficiently above the labeled weight so that each can will have at least the labeled weight packed thereinto. If the weight control of the machine is poor, such that a relatively large variation in weight occurs from can to can, then many cans will have a considerable excess of fish. Such excess either represents a loss to the canner, or a loss to the consumer if the cost of the excess fish is passed on. The better the weight control per can, the less the amount of variable excess fish per can.
In machines as described above, weight control is typically accomplished by filling each metering pocket with the same volume of fish, the fish being compressed by as uniform a pressure as possible so that the density and weight per can will be constant. This compression force is supplied by the reciprocating ram in the feed chute.
As mentioned previously, a drag exists between the feed chute walls and the fish which must be overcome by the ram to feed the fish through the chute. This drag resistance varies somewhat during the course of a run. Since the ram force is used both to overcome a variable drag resistance and to compress the fish in the metering pocket, the variation in drag force will cause a variation in compression force and thereby affect the weight control. The greater the proportion of ram force used to overcome drag resistance to total ram force, the poorer the weight control.
Machines of the type having necessarily restricted-size feed chutes, have a considerable drag and a correspondingly poor weight control.
The effect of the variable drag on weight control can be reduced by increasing the total ram force so that the force required to overcome drag becomes a lesser portion of the total force. However, if this is done, then the likelihood of damage to the fish will increase. In addition, an increase in ram force will produce an adverse effect on another aspect of weight control, namely, the amount of fish protein that is to be packed into each can.
Fish flesh contains considerable protein-containing fluid which may be squeezed out of the flesh when the fish is subjected to pressure. An increase in ram force will increase the compression on the fish. If the compression becomes excessive, this fluid will be squeezed out in the chute or metering pockets and lost, so that the canned product will not meet the labelled weight. In such case, supplemental fish flesh must be added to the can. As a consequence, increasing the ram force in an effort to provide better control of the weight of fish per can will instead produce an adverse effect.
It is the principal object of the present invention to provide a fish-canning machine for solid pack tuna which will substantially increase the production capacity while at the same time enabling the production of a higher quality pack with better weight control and increased yield due to less fluid loss.